feat(#39): format large numbers with compact display (1.2B, 900M, etc.)

src/pages/Crypto.jsx

@@ -3,11 +3,11 @@
  * ----------------------
  * Easy:
  *  - [ ] Sort buttons (Market Cap, Price, 24h %)
- *  - [ ] Show coin symbol & small logo (image URL in API)
- *  - [ ] Format numbers with utility (abbreviate large caps: 1.2B)
- *  - [ ] Highlight positive vs negative 24h change (green/red)
+ *  - [x] Show coin symbol & small logo (image URL in API)
+ *  - [x] Format numbers with utility (abbreviate large caps: 1.2B)
+ *  - [x] Highlight positive vs negative 24h change (green/red)
  * Medium:
- *  - [ ] Add pagination (Top 50 -> allow next pages)
+ *  - [x] Add pagination (Top 50 -> allow next pages)
  *  - [ ] Client-side caching with timestamp (avoid re-fetch spam)
  *  - [ ] Mini sparkline (use canvas or simple SVG)
  *  - [ ] Favorites (star) + localStorage persistence
@@ -18,10 +18,12 @@
  *  - [ ] Dark mode adaptive coloring for charts
  *  - [ ] Extract to service + custom hook (useCryptoMarkets)
  */
+
 import { useEffect, useState } from "react";
 import Loading from "../components/Loading.jsx";
 import ErrorMessage from "../components/ErrorMessage.jsx";
 import Card from "../components/Card.jsx";
+import formatNumber from "../utilities/numberFormatter.js";
 
 export default function Crypto() {
   const [coins, setCoins] = useState([]);
@@ -57,30 +59,61 @@ export default function Crypto() {
 
   return (
     <div>
-      <h2>Cryptocurrency Tracker</h2>
+      <h2>💹 Cryptocurrency Tracker</h2>
       <input
         value={query}
         onChange={(e) => setQuery(e.target.value)}
-        placeholder="Search coin"
+        placeholder="Search coin..."
+        style={{ marginBottom: "1rem" }}
       />
 
       {loading && <Loading />}
       <ErrorMessage error={error} />
+
       <div className="grid">
-        {filtered.map((c) => (
-          <Card
-            key={c.id}
-            title={c.name}
-            footer={<span>${c.current_price}</span>}
-          >
-            <p>Market Cap: ${c.market_cap.toLocaleString()}</p>
-            <p>24h: {c.price_change_percentage_24h?.toFixed(2)}%</p>
-            {/* TODO: Add mini sparkline chart */}
-          </Card>
-        ))}
+        {filtered.map((c) => {
+          const isPositive = c.price_change_percentage_24h >= 0;
+          return (
+            <Card
+              key={c.id}
+              title={
+                <span style={{ display: "flex", alignItems: "center", gap: 8 }}>
+                  <img
+                    src={c.image}
+                    alt={c.symbol}
+                    style={{ width: 24, height: 24, borderRadius: "50%" }}
+                  />
+                  {c.name} ({c.symbol.toUpperCase()})
+                </span>
+              }
+              footer={<strong>${c.current_price.toLocaleString()}</strong>}
+            >
+              <p>Market Cap: ${formatNumber(c.market_cap)}</p>
+              <p
+                style={{
+                  color: isPositive ? "#16a34a" : "#dc2626",
+                  fontWeight: 600,
+                }}
+              >
+                24h: {isPositive ? "+" : ""}
+                {c.price_change_percentage_24h?.toFixed(2)}%
+              </p>
+              {/* TODO: Add mini sparkline chart */}
+            </Card>
+          );
+        })}
       </div>
 
-      <div className="pagination">
+      <div
+        className="pagination"
+        style={{
+          display: "flex",
+          justifyContent: "center",
+          alignItems: "center",
+          gap: "1rem",
+          marginTop: "1.5rem",
+        }}
+      >
         <button onClick={() => setPage((p) => p - 1)} disabled={page === 1}>
           Previous
         </button>

src/utilities/numberFormatter.js

@@ -0,0 +1,9 @@
+export default function formatNumber(number) {
+  return new Intl.NumberFormat("en", {
+    notation: "compact",
+
+    maximumFractionDigits: 1,
+  }).format(number);
+}
+
+// TODO: we can make here different type of currency